There has been obtained a digitized radiographic image from subjects by the radiation image conversion method using a radiation image conversion panel having a stimulable phosphor layer. This radiation image conversion method is a process in which radiation rays having transmitted a subject are exposed onto the stimulable phosphor layer, whereby radiation-energy corresponding to the radiation transmission density of the respective portions of the subject is accumulated in a stimulable phosphor, thereafter, the radiation energy accumulated in the stimulable phosphor is emitted as photo-stimulated luminescence by excitation of stimulating light and the strength of the stimulated luminescence is converted to an electric signal, which is further converted to a visible image through imaging materials such as photographic material or an image display such as a CRT (Cathode Ray Tube) or a LCD (liquid Crystal Display).
It is well known that formation of a stimulable phosphor on a support by vapor-depositing a stimulable phosphor comprised of CsBr as a parent component has achieved a radiation image conversion panel exhibiting greatly enhanced sensitivity.
It is also known that constituting a stimulable phosphor layer with minute columnar crystals results in excellent sharpness. Since the minute columnar crystals exhibit a light-induced effect, in such a stimulable phosphor layer, stimulated luminescence is repeatedly reflected within the columnar crystals and reaches the bottom of the columnar crystals, while preventing the stimulated luminescence from scattering, thereby resulting in enhanced sharpness of the image formed by stimulated luminescence. As is disclosed in JP-A No. 5-249298 (hereinafter, the term “JP-A” refers to a Japanese Patent Application Publication), it is known to be effective to make uniform the direction of internal crystal growth in the stimulable phosphor layer, specifically at the time of forming the columnar crystals.